Enhanced recovery of useful coal, potassium chloride and borax from screen bowl centrifuge

ABSTRACT

A method of enhancing the recovery of useful coal or potassium chloride or borax from screenbowl centrifuge separation operations comprising adding to the screenbowl centrifuge, from about 0.03 lbs active polymer/ton dry solids in centrifuge to about 0.70 lbs active polymer/ton dry solids in centrifuge, of a cationic terpolymer, wherein said cationic terpolymer is prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.1 to about 10 mole percent of one or more hydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent of one or more nonionic monomers.

FIELD OF THE INVENTION

This invention is in the field of mining and processing of coal,potassium chloride and borax. More particularly this invention concernsthe use of polymers to enhance recovery of useful coal, potassiumchloride and borax in screen bowl centrifuge separation operations.

BACKGROUND OF THE INVENTION

In processing of coal and potassium chloride and borax it is typical touse a one or more solid-liquid separation stages in order to isolate thedesired solids. In all of these mining processing applications, thefinest fractions of solid-liquid slurries may be subjected to screenbowl centrifugation for recovery of dewatered solids. The screenbowlcentrifuge in a coal or potassium chloride or borax processing plant isused to remove the moisture from the coal or potassium chloride orborax. As part of the moisture removal some of the solids, usually about−40 microns in size, are lost.

The screenbowl centrifuge rotates at a very high rpm. The slurry of coalor potassium chloride or borax enters through the feed pipe anddischarges inside the machine. The solids accelerate to the high rpm ofthe machine and thus encounter high centrifugal forces. This causes thesolids to move to the outside of machine and the solids are then movedtoward the discharge by an auger. The liquid moves in the oppositedirection and discharges as “effluent” at the “bowl drain”. The effluentis typically sent to waste and thus the useful coal, potassium chlorideor borax. in the effluent is lost. That is the waste that miningprocessing is trying to reduce. A small fraction of the liquid leavesthe centrifuge at the screen drain, however, that is not the fraction ofinterest in this work because the amount of screen drain liquid isrelatively small compared to the effluent and the screen drain liquidtypically is recycled back through the process.

The separation inside the machine is made at about 40 microns; greaterthan about 98% of the +40 micron material reports to the discharge asproduct along with about 50-70% of the −40 micron material. Theremaining about 30-50% of the −40 micron solids report to the effluentand are discarded.

In these separations, it is always a goal to increase the amount ofuseful coal, potassium chloride and borax that is recovered.

In the past when flocculants were added to the feed prior to enteringthe machine, the high centrifugal forces inside the machine resulted inthe flocculants being sheared, and thus they were not effective incapturing more solids. Therefore, it is widely accepted in the industrythat flocculant addition is not effective in reducing the amount ofsolids being discharged in the effluent.

It would be desirable to identify materials capable of flocculatingcoal, potassium chloride and borax within the high shear conditions of acentrifuge separation.

SUMMARY OF THE INVENTION

The first aspect of the instant claimed invention is a method ofenhancing the recovery of useful coal from screenbowl centrifugeseparation operations comprising adding to the screenbowl centrifuge,from about 0.03 lbs active polymer/ton dry solids in centrifuge to about0.70 lbs active polymer/ton dry solids in centrifuge, of a cationicterpolymer, wherein said cationic terpolymer is prepared by polymerizingfrom about 1 to about 99.1 mole percent of one or more cationicmonomers, from about 0.1 to about 10 mole percent of one or morehydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent ofone or more nonionic monomers.

The second aspect of the instant claimed invention is a method ofenhancing the recovery of useful potassium chloride from screenbowlcentrifuge separation operations comprising adding to the screenbowlcentrifuge, from about 0.03 lbs active polymer/ton dry solids incentrifuge to about 0.70 lbs active polymer/ton dry solids incentrifuge, of a cationic terpolymer to the screenbowl centrifuge,wherein said cationic terpolymer is prepared by polymerizing from about1 to about 99.1 mole percent of one or more cationic monomers, fromabout 0.1 to about 10 mole percent of one or morehydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent ofone or more nonionic monomers.

The third aspect of the instant claimed invention is a method ofenhancing the recovery of useful borax from screenbowl centrifugeseparation operations comprising adding to the screenbowl centrifuge,from about 0.03 lbs active polymer/ton dry solids in centrifuge to about0.70 lbs active polymer/ton dry solids in centrifuge, of a cationicterpolymer, wherein said cationic terpolymer is prepared by polymerizingfrom about 1 to about 99.1 mole percent of one or more cationicmonomers, from about 0.1 to about 10 mole percent of one or morehydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent ofone or more nonionic monomers.

DETAILED DESCRIPTION OF THE INVENTION

Throughout this patent application, the following terms have theindicated meanings.

“AM” means acrylamide.

“Alkyl” means a monovalent group derived from a straight or branchedchain saturated hydrocarbon by the removal of a single hydrogen atom.Representative alkyl groups include methyl, ethyl, n- and iso-propyl,and the like.

“Alkylene” means a divalent group derived from a straight or branchedchain saturated hydrocarbon by the removal of two hydrogen atoms.Representative alkylene groups include methylene, ethylene, propylene,and the like.

“Based on polymer active” and “based on monomer” mean the amount of areagent added based on the level of vinylic monomer in the formula, orthe level of polymer formed after polymerization, assuming 100%conversion.

“Based on formula” means the amount of reagent added based on the totalformula weight.

“borax” is a natural hydrated sodium borate, (either 5 or 10 H₂O) thatis found in salt lakes and alkali soils. It is also the commercial namefor sodium borate.

“Cationic Monomer” means a monomer, as defined herein, which possesses anet positive charge. Representative cationic monomers includedialkylaminoalkyl acrylates and methacrylates and their quaternary oracid salts, including, but not limited to, dimethylaminoethyl acrylatemethyl chloride quaternary salt, dimethylaminoethyl acrylate methylsulfate quaternary salt, dimethyaminoethyl acrylate benzyl chloridequaternary salt, dimethylaminoethyl acrylate sulfuric acid salt,dimethylaminoethyl acrylate hydrochloric acid salt, dimethylaminoethylmethacrylate methyl chloride quaternary salt, dimethylaminoethylmethacrylate methyl sulfate quaternary salt, dimethylaminoethylmethacrylate benzyl chloride quaternary salt, dimethylaminoethylmethacrylate sulfuric acid salt, dimethylaminoethyl methacrylatehydrochloric acid salt, dialkylaminoalkylacrylamides or methacrylamidesand their quaternary or acid salts such asacrylamidopropyltrimethylammonium chloride,dimethylaminopropylacrylamide methyl sulfate quaternary salt,dimethylaminopropylacrylamide sulfuric acid salt,dimethylaminopropylacrylamide hydrochloric acid salt,methacrylamidopropyltrimethylammonium chloride,dimethylaminopropylmethacrylamide methyl sulfate quaternary salt,dimethylaminopropylmethacrylamide sulfuric acid salt,dimethylaminopropylmethacrylamide hydrochloric acid salt,diethylaminoethyl acrylate, diethylaminoethyl methacrylate,diallyldiethylammonium chloride and diallyldimethyl ammonium chloride.Alkyl groups are generally C₁₋₄ alkyl.

“Chain Transfer Agent” means any molecule, used in free-radicalpolymerization, which will react with a polymer radical forming a deadpolymer and a new radical. Representative Chain Transfer Agents arelisted by K. C. Berger and G. Brandrup, “Transfer Constants to Monomer,Polymer, Catalyst, Solvent, and Additive in Free RadicalPolymerization,” Section II, pp. 81-151, in “Polymer Handbook,” editedby J. Brandrup and E. H. Immergut, 3d edition, 1989, John Wiley & Sons,New York. Preferred chain transfer agents include sodium formate,2-mercaptoethanol and isopropanol. Sodium formate is more preferred.

“Coal” means a natural, solid, combustible material formed fromprehistoric plant life which occurs in layers or veins in sedimentaryrocks. Chemically, coal is a macromolecular network composed of groupsof polynuclear aromatic rings, to which are attached subordinate ringsconnected to oxygen, sulfur and aliphatic bridges.

“Dispersion polymer” means a dispersion of fine particles of polymer inan aqueous salt solution which is prepared by polymerizing monomers withstirring in an aqueous salt solution in which the resulting polymer isinsoluble. See U.S. Pat. Nos. 5,708,071; 4,929,655; 5,006,590;5,597,859; 5,597,858 and European Patent nos. 657,478 and 630,909.

In a typical procedure for preparing a dispersion polymer, an aqueoussolution containing one or more inorganic or hydrophobic salts, one ormore water-soluble monomers, any polymerization additives such asprocessing aids, chelants, pH buffers and a water-soluble stabilizerpolymer is charged to a reactor equipped with a mixer, a thermocouple, anitrogen purging tube, and a water condenser. The monomer solution ismixed vigorously, heated to the desired temperature, and then awater-soluble initiator is added. The solution is purged with nitrogenwhile maintaining temperature and mixing for several hours. After thistime, the mixture is cooled to room temperature, and anypost-polymerization additives are charged to the reactor. Watercontinuous dispersions of water-soluble polymers are free flowingliquids with product viscosities generally 100-10,000 cP, measured atlow shear.

“Gel polymer” means a polymer made by gel polymerization. In a typicalprocedure for preparing gel polymers, an aqueous solution containing oneor more water-soluble monomers and any additional polymerizationadditives such as chelants, pH buffers, and the like, is prepared. Thismixture is charged to a reactor equipped with a mixer, a thermocouple, anitrogen purging tube and a water condenser. The solution is mixedvigorously, heated to the desired temperature, and then one or morewater-soluble free radical polymerization initiators are added. Thesolution is purged with nitrogen while maintaining temperature andmixing for several hours. Typically, the viscosity of the solutionincreases during this period. After the polymerization is complete, thereactor contents are cooled to room temperature and then transferred tostorage. Gel polymer viscosities vary widely, and are dependent upon theconcentration and molecular weight of the active polymer component. Gelpolymers may be dried to yield dry polymers.

“DMAEA*MCQ” means dimethylaminoethyl acrylate methyl chloride quaternarysalt. This may also be abbreviated “DMAEA.MCQ”.

“Hydroxyalkyl(meth)acrylate” means a compound of formula

where R₁ is H or CH₃ and L is C₁-C₈, preferably C₁-C₄ alkylene.Representative hydroxyalkyl(meth)acrylates include hydroxyethylacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate,and the like.

“Latex polymer” means a water-in-oil polymer emulsion comprising acationic terpolymer according to this invention in the aqueous phase, ahydrocarbon oil for the oil phase and one or more water-in-oilemulsifying agents. Latex polymers are hydrocarbon continuous with thewater-soluble polymers dispersed within the hydrocarbon matrix. Thelatex polymer is “inverted” or activated for use by releasing thepolymer from the particles using shear, dilution, and, generally,another surfactant. See U.S. Pat. No. 3,734,873, incorporated herein byreference. Representative preparations of high molecular weight inverseemulsion polymers are described in U.S. Pat. Nos. 2,982,749; 3,284,393;and 3,734,873. See also, “Mechanism, Kinetics and Modeling of theInverse-Microsuspension Homopolymerization of Acrylamide,” Hunkeler, etal., Polymer (1989), 30(1), 127-42; and “Mechanism, Kinetics andModeling of Inverse-Microsuspension Polymerization: 2. Copolymerizationof Acrylamide with Quaternary Ammonium Cationic Monomers,” Hunkeler etal., Polymer (1991), 32(14), 2626-40.

Inverse emulsion polymers are prepared by dissolving the desiredmonomers and any polymerization additives such as inorganic salts,chelants, pH buffers, and the like in the aqueous phase, dissolving theemulsifying agent(s) in the oil phase, emulsifying the water phase inthe oil phase to prepare a water-in-oil emulsion, in some cases,homogenizing the water-in-oil emulsion, polymerizing the monomersdissolved in the water phase of the water-in-oil emulsion to obtain thepolymer as a water-in-oil emulsion. If so desired, a self-invertingsurfactant can be added after the polymerization is complete in order toobtain the water-in-oil self-inverting emulsion.

The oil phase comprises any inert hydrophobic liquid. Preferredhydrophobic liquids include aliphatic and aromatic hydrocarbon liquidsincluding benzene, xylene, toluene, paraffin oil, coal, potassiumchloride or borax spirits, kerosene, naphtha, and the like. A paraffinicoil is preferred.

Free radical yielding initiators such as benzoyl peroxide, lauroylperoxide, 2,2′-azobis (isobutyronitrile) (AIBN),2,2′-azobis(2,4-dimethylvaleronitrile) (AIVN), potassium persulfate andthe like are useful in polymerizing vinyl and acrylic monomers.2,2′-azobis(isobutyronitrile) (AIBN) and2,2′-azobis(2,4-dimethylvaleronitrile) (AIVN) are preferred. Theinitiator is utilized in amounts ranging between about 0.002 and about0.2 percent by weight of the monomers, depending upon the solubility ofthe initiator.

Water-in-oil emulsifying agents useful for preparing latex polymersinclude sorbitan esters of fatty acids, ethoxylated sorbitan esters offatty acids, and the like or mixtures thereof. Preferred emulsifyingagents include sorbitan monooleate, polyoxyethylene sorbitanmonostearate, and the like. Additional details on these agents may befound in McCutcheon's Detergents and Emulsifiers, North AmericanEdition, 1980. Any inverting surfactant or inverting surfactant mixturedescribed in the prior art may be used. Representative invertingsurfactants include ethoxylated nonylphenol, ethoxylated linearalcohols, and the like. Preferred inverting surfactants are ethoxylatedlinear alcohols.

The polymer is prepared by polymerizing the appropriate monomers at atemperature of from about 30° C. to about 85° C. over about 1 to about24 hours, preferably at a temperature of from about 40° C. to about 70°C. over about 3 to about 6 hours. Upon completion of the reaction, thewater-in-oil emulsion polymer is cooled to room temperature, where anydesired post-polymerization additives, such as antioxidants, or a highHLB surfactant (as described in U.S. Pat. No. 3,734,873) may be added.

The resulting emulsion polymer is a free-flowing liquid. An aqueoussolution of the water-in-oil emulsion polymer can be generated by addinga desired amount of the emulsion polymer to water with vigorous mixingin the presence of a high-HLB surfactant (as described in U.S. Pat. No.3,734,873).

“lbs” means pounds. One pound is equal to 454 grams is equal 0.454kilograms.

“Monomer” means a polymerizable allylic, vinylic or acrylic compound.The monomer may be cationic or nonionic. Vinyl monomers are preferred,acrylic monomers are more preferred.

“Nalco” means Nalco Company, 1601 W. Diehl Road, Naperville, Ill. 60563.(630) 305-1000.

“Nonionic monomer” means a monomer as defined herein which iselectrically neutral. Representative non-ionic, water-soluble monomersinclude acrylamide, methacrylamide, N,N-dimethylacrylamide,N,N-diethylacrylamide, N-isopropylacrylamide, N-vinylformamide,N-vinylmethylacetamide, N-vinyl pyrrolidone, N-t-butylacrylamide,N-methylolacrylamide, and the like. Preferred nonionic monomers areacrylamide and methacrylamide. Acrylamide is more preferred.

“potassium chloride” is KCl, Chemical Abstract Services Registry No.7447-40-7. For purposes of this patent application the word “Potash” isunderstood to be a source of potassium chloride. Potash is currentlybeing mined in New Mexico, U.S.A. and in Saskatchewan, Canada.

“RSV” stands for Reduced Specific Viscosity. The RSV of a polymersolution is a measure of the capacity of polymer molecules to enhancethe viscosity of the solution at a given concentration, which depends onthe structure of the polymer molecules (including size and shape), andinteraction between polymer molecules. Within a series of polymerhomologs which are substantially linear and well solvated, “reducedspecific viscosity (RSV)” measurements for dilute polymer solutions arean indication of polymer chain length and average molecular weightaccording to Paul J. Flory, in “Principles of Polymer Chemistry”,Cornell University Press, Ithaca, N.Y., 1953, Chapter VII,“Determination of Molecular Weights”, pp. 266-316. The RSV is measuredat a given polymer concentration and temperature and calculated asfollows:${RSV} = \frac{\left\lbrack {\left( \frac{\eta}{\eta_{o}} \right) - 1} \right)}{c}$wherein η=viscosity of polymer solution;

-   -   η_(o)=viscosity of solvent at the same temperature; and    -   c=concentration of polymer in solution.        The units of concentration “c” are (grams/100 ml or        g/deciliter). Therefore, the units of RSV are dL/g. In this        patent application, for measuring RSV, the solvent used is 1.0        molar sodium nitrate solution. The polymer concentration in this        solvent is 0.045 g/dL. The RSV is measured at 30° C. The        viscosities η and η_(o) are measured using a Cannon Ubbelohde        semimicro dilution viscometer, size 75. The viscometer is        mounted in a perfectly vertical position in a constant        temperature bath adjusted to 30±0.02° C. The error inherent in        the calculation of RSV is about 2 dl/grams. When two polymer        homologs within a series have similar RSV's that is an        indication that they have similar molecular weights.

“ton” means 2000 pounds.

The instant claimed invention is a method of enhancing the recovery ofuseful mined materials from screenbowl centrifuge separation operationscomprising adding to the screenbowl centrifuge, from about 0.03 lbsactive polymer/ton dry solids in centrifuge to about 0.70 lbs activepolymer/ton dry solids in centrifuge, of a cationic terpolymer, whereinsaid cationic terpolymer is prepared by polymerizing from about 1 toabout 99.1 mole percent of one or more cationic monomers, from about 0.1to about 10 mole percent of one or more hydroxyalkyl(meth)acrylates andfrom one to about 98.1 mole percent of one or more nonionic monomers.

The useful mined materials are selected from the group consisting ofcoal, potassium chloride and borax.

The screenbowl centrifuge separation operations can be any part of thecoal, potassium chloride or borax process where a screenbowl centrifugeis used in the separation. For instance, in coal processing, typicallythe screenbowl centrifuge in a coal processing plant is used to removethe moisture from the coal, prior to the finished coal leaving the coalprocessing plant.

The streams associated with a screenbowl include the feed, the effluent,the screen drain and the product.

“Feed” is the minus 1 mm material at 25-35% solids that enters thescreenbowl. The flow varies from about 350 to about 800 gallons perminute depending on the size of the machine. The percent solids can varyfrom about 20% to about 40% and the tons per hour of solids can be fromabout 20 to about 80.

“Effluent” is the water and fine solids that are removed from the coal.The solids in the effluent are usually 96-98% minus 40 microns. The flowcan be 250-500 gpm and the tons/hr of solids depends upon the % solids.This material normally reports to the refuse thickener for disposal.This is the material that the instant claimed invention is directed toas the instant claimed invention will permit more useful coal orpotassium chloride or borax to leave the screen bowl centrifuge with theproduct instead of leaving the screen bowl centrifuge with the effluent.

“Screen Drain” is entrained water and fine solids that are removed justprior to the coal discharging the machine. The flow is usually small,about 5% of the feed flow, and this material is recycled back into theplant.

“Product” is the dried coal or the dried potassium chloride or the driedborax to be sold.

The screenbowl rotates at a very high rpm. The coal slurry entersthrough the feed pipe and discharges inside the machine. The solidsaccelerate to the high rpm of the machine and thus encounter highcentrifugal forces. This causes the solids to move to the outside ofmachine and the solids are then moved toward the discharge by an auger.The liquid moves in the opposite direction and discharges at the feedend. The separation inside the machine is made at about 40 microns;greater than 98% of the +40 micron material reports to the discharge asproduct along with about 50-60% of the −40 micron material. Theremaining 40-50% of the −40 micron solids report to the effluent and arediscarded.

The cationic terpolymers are added to the screenbowl for the purpose ofcapturing more of the solids from the effluent and thus having it reportwith the Product. In the past when flocculants were added to the feedprior to entering the machine, the high forces inside the machineresulted in the flocculants being sheared, and thus they were noteffective in capturing more solids. Therefore, it was widely accepted inthe industry that any type of flocculant addition was not effective inreducing the amount of solids being discharged in the effluent. Incontrast to what was believed to be true, with use of the cationicterpolymers described herein, it has been found possible to enhance therecovery of desired coal, potassium chloride or borax by using thecationic terpolymers in centrifuge separation operations.

The cationic terpolymers can be made by latex polymerization, gelpolymerization and dispersion polymerization techniques. It is preferredthat they be made by latex polymerization, for convenience ofapplication, and thus latex polymers are preferred for use in theinstant claimed invention.

Regarding the polymers, the cationic polymers useful in the instantclaimed invention are prepared by polymerizing from about 1 to about99.1 mole percent of one or more cationic monomers, from about 0.1 toabout 10 mole percent of one or more hydroxyalkyl(meth)acrylates andfrom one to about 98.1 mole percent of one or more nonionic monomers.

In one preferred aspect, the cationic polymer is prepared bypolymerizing from about 20 to about 80 mole percent of one or morecationic monomers, from about 1 to about 2.5 mole percent of one or morehydroxyalkyl(meth)acrylates and from 17.5 to about 79 mole percent ofone or more nonionic monomers.

In another preferred aspect the cationic monomer is selected from thegroup comprising dimethylaminoethyl acrylate methyl chloride quaternarylsalt, dimethylaminoethyl methacrylate methyl chloride quaternary salt,acrylamidopropyltrimethylammonium chloride andmethacrylamidopropyltrimethylammonium chloride. Dimethylaminoethylacrylate methyl chloride quaternary salt is the most preferred cationicmonomer.

In another preferred aspect, the hydroxyalkyl(meth)acrylate is selectedfrom hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutylacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and6-hydroxyhexyl methacrylate. 2-Hydroxyethyl methacrylate (hereinafter“HEMA”) and 2-hydroxypropyl methacrylate are more preferred. HEMA is themost preferred hydroxyalkyl(meth)acrylate.

In another preferred aspect of this invention, the nonionic monomers areselected from acrylamide and methacrylamide and the cationic monomersare selected from dimethylaminoethyl acrylate methyl chloride quaternarysalt, dimethylaminoethyl methacrylate methyl chloride quaternary salt,acrylamidopropyltrimethylammonium chloride andmethacrylamidopropyltrimethylammonium chloride.

In another preferred aspect, the nonionic monomer is acrylamide and thecationic monomer is dimethylaminoethyl acrylate methyl chloridequaternary salt and the hydroxyalkyl(meth)acrylate is hydroxyethylmethacrylate.

The cationic terpolymers useful in the instant claimed invention areeither available commercially or may be synthesized using techniquesknown to people of ordinary skill in the art. See U.S. Pat. No.6,627,719 B2, entitled CATIONIC LATEX TERPOLYMERS FOR SLUDGE DEWATERING,which issued on Sep. 30, 2003. U.S. Pat. No. 6,627,719 B2 isincorporated by reference in its entirety.

Cationic terpolymers of the following formulas are available from Nalco.Polymer A B C D E Mole % AM 70 49 34 20 50 Mole % DMAEA * MCQ 29 49 6478 49 Mole % HEMA 1 2 2 2 1 Total Mole % 100 100 100 100 100

The total amount of polymer required to effectively enhance the recoveryof useful coal, potassium chloride or borax from centrifuge separationmay vary considerably according to the characteristics of the materialbeing fed into the screenbowl centrifuge and the degree of processing inthe centrifuge required.

Typically, the polymer is added in an amount of from about 0.03 lbsactive polymer/ton dry solids in centrifuge to about 0.70 lbs activepolymer/ton dry solids in centrifuge, preferably from about 0.04 lbsactive polymer/ton dry solids into centrifuge to about 0.68 lbs activepolymer/ton dry solids in centrifuge, and more preferably from about 0.1lbs active polymer/ton dry solids in centrifuge to about 0.3 lbs activepolymer/ton dry solids into centrifuge based on polymer actives.

The dose of polymer based on lbs active polymer/lbs slurry incentrifuge, expressed in ppm, is as follows: the polymer is added in anamount of from about 5 ppm to about 125 ppm, preferably from about 10ppm to about 100 ppm and more preferably from about 20 ppm to about 80ppm based on polymer actives.

To enhance the efficacy of the cationic terpolymers of the instantclaimed invention it is recommended to add the polymers inside thecentrifuge in a low-shear zone to allow the solids to be flocculatedwithout being torn apart by the shear forces. Preferably, the polymersare added after water and fine sized solids were separated from thelarger coal particle. It is not recommended to add the polymers with thefeed into the screenbowl centrifuge because if this is done, then anypositive effect the polymers have upon the feed in terms of flocculationwill be negated when the newly formed flocs encounter the severe shearin the centrifuge.

Addition of polymer to centrifuge may be through pipes or drop chutes orany other technique known in the art.

In addition to enhancing the recovery of coal, use of the cationicterpolymers of this invention has also been found possible to enhancethe recovery of potassium chloride and borax.

The second aspect of the instant claimed invention is a method ofenhancing the recovery of useful potassium chloride from screenbowlcentrifuge separation operations comprising adding to the screenbowlcentrifuge, from about 0.03 lbs active polymer/ton dry solids incentrifuge to about 0.70 lbs active polymer/ton dry solids incentrifuge, of a cationic terpolymer, wherein said cationic terpolymeris prepared by polymerizing from about 1 to about 99.1 mole percent ofone or more cationic monomers, from about 0.1 to about 10 mole percentof one or more hydroxyalkyl(meth)acrylates and from one to about 98.1mole percent of one or more nonionic monomers.

Potassium chloride is mined from sylvite deposits, known as Potash, inNew Mexico and Saskatchewan and purified by fractional crystallizationor flotation. It can also be crystallized from salt lake brine andpurified by recyrstallization. A thorough review article of processingof potash in the mines of Saskatchewan can be found in CIM Bulletin,Vol. 96, No. 1070, pgs. 61-65, “Potash Processing in Saskatchewan—Areview of process technologies” by C. F. Perucca, April 2003.

When potash is being processed to yield potassium chloride, screen-bowlcentrifuges are used to de-brine the concentrates from flotation bearingthe valuable coal, potassium chloride or borax. The concentrate is thendried and compacted to afford granular product for fertilizerapplications or is redissolved and crystallized to afford industrialgrade potassium chloride.

The third aspect of the instant claimed invention is a method ofenhancing the recovery of useful borax from screenbowl centrifugeseparation operations comprising adding to the screenbowl centrifuge,from about 0.03 lbs active polymer/ton dry solids in centrifuge to about0.70 lbs active polymer/ton dry solids in centrifuge, of a cationicterpolymer, wherein said cationic terpolymer is prepared by polymerizingfrom about 1 to about 99.1 mole percent of one or more cationicmonomers, from about 0.1 to about 10 mole percent of one or morehydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent ofone or more nonionic monomers.

Borax is a naturally hydrated sodium borate found in salt lakes andalkali soils. When borax is being processed, mud tailings areconcentrated in screen bowl centrifuges for impoundment.

The performance of the cationic terpolymers of this invention may bemonitored by means of an inert fluorescent tracer as described in U.S.Pat. No. 4,783,314, incorporated herein by reference. In particular, acomposition comprising a cationic terpolymer according to this inventionand an inert fluorescent tracer compound in a known ratio is added tothe screenbowl centrifuge containing the coal, potassium chloride orborax slurry as described above. The fluorescent signal of the coal,potassium chloride or borax slurry is detected and measured using one ormore fluorometers and used to quantify and control the amount and feedrate of the polymer to achieve the desired amount of cationic terpolymerin the coal, potassium chloride or borax slurry.

“Inert fluorescent tracer compound” means a material which is capable offluorescing while present in the sludge being treated. The inertfluorescent tracer compound should not be appreciably affected by anyother material present in the coal, potassium chloride or borax slurry,or by the temperature or temperature changes encountered during thedewatering process. Inert fluorescent tracers suitable for use with thecationic terpolymers of the instant claimed invention are selected fromthe group comprising:

-   -   1-deoxy-1-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)-D-ribitol,        also known as Riboflavin or Vitamin B2 (CAS Registry No.        83-88-5),    -   fluorescein (CAS Registry No. 2321-07-5),    -   fluorescein, sodium salt (CAS Registry No. 518-47-8, aka Acid        Yellow 73, Uranine),    -   2-anthracenesulfonic acid sodium salt (CAS Registry No.        16106-40-4),    -   1,5-anthracenedisulfonic acid (CAS Registry No. 61736-91-2) and        salts thereof,    -   2,6-anthracenedisulfonic acid (CAS Registry No. 61736-95-6) and        salts thereof,    -   1,8-anthracenedisulfonic acid (CAS Registry No. 61736-92-3) and        salts thereof,    -   mono-, di-, or tri-sulfonated napthalenes, including but not        limited to        -   1,5-naphthalenedisulfonic acid, disodium salt (hydrate) (CAS            Registry No. 1655-29-4, aka 1,5-NDSA hydrate),        -   2-amino-1-naphthalenesulfonic acid (CAS Registry No.            81-16-3),        -   5-amino-2-naphthalenesulfonic acid (CAS Registry No.            119-79-9),        -   4-amino-3-hydroxy-1-naphthalenesulfonic acid (CAS Registry            No. 90-51-7),        -   6-amino-4-hydroxy-2-naphthalenesulfonic acid (CAS Registry            No. 116-63-2),        -   7-amino-1,3-naphthalenesulfonic acid, potassium salt (CAS            Registry No. 79873-35-1),        -   4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid (CAS            Registry No. 90-20-0),        -   5-dimethylamino-1-naphthalenesulfonic acid (CAS Registry No.            4272-77-9),        -   1-amino-4-naphthalene sulfonic acid (CAS Registry No.            84-86-6),        -   1-amino-7-naphthalene sulfonic acid (CAS Registry No.            119-28-8), and        -   2,6-naphthalenedicarboxylic acid, dipotassium salt (CAS            Registry No. 2666-06-0),    -   3,4,9,10-perylenetetracarboxylic acid (CAS Registry No.        81-32-3),    -   C.I. Fluorescent Brightener 191, also known as, Phorwite CL (CAS        Registry No. 12270-53-0),    -   C.I. Fluorescent Brightener 200, also known as Phorwite BKL (CAS        Registry No. 61968-72-7),    -   benzenesulfonic acid,        2,2′-(1,2-ethenediyl)bis[5-(4-phenyl-2H-1,2,3-triazol-2-yl)-,        dipotassium salt, also known as Phorwite BHC 766 (CAS Registry        No. 52237-03-3),    -   benzenesulfonic acid,        5-(2H-naphtho[1,2-d]triazol-2-yl)-2-(2-phenylethenyl)-, sodium        salt, also known as Pylaklor White S-15A (CAS Registry No.        6416-68-8),    -   1,3,6,8-pyrenetetrasulfonic acid, tetrasodium salt (CAS Registry        No. 59572-10-0),    -   pyranine, (CAS Registry No. 6358-69-6, aka        8-hydroxy-1,3,6-pyrenetrisulfonic acid, trisodium salt),    -   quinoline (CAS Registry No. 91-22-5),    -   3H-phenoxazin-3-one, 7-hydroxy-, 10-oxide, also known as        Rhodalux (CAS Registry No. 550-82-3),    -   xanthylium, 9-(2,4-dicarboxyphenyl)-3,6-bis(diethylamino)-,        chloride, disodium salt, also known as Rhodamine WT (CAS        Registry No. 37299-86-8),    -   phenazinium, 3,7-diamino-2,8-dimethyl-5-phenyl-, chloride, also        known as Safranine O (CAS Registry No. 477-73-6),    -   C.I. Fluorescent Brightener 235, also known as Sandoz CW (CAS        Registry No. 56509-06-9),    -   benzenesulfonic acid,        2,2′-(1,2-ethenediyl)bis[5-[[4-[bis(2-hydroxyethyl)amino]-6-[(4-sulfophenyl)amino]-1,3,5-triazin-2-yl]amino]-,        tetrasodium salt, also known as Sandoz CD (CAS Registry No.        16470-24-9, aka Flu. Bright. 220),    -   benzenesulfonic acid,        2,2′-(1,2-ethenediyl)bis[5-[[4-[(2-hydroxypropyl)amino]-6-(phenylamino)-1,3,5-triazin-2-yl]amino]-,        disodium salt, also known as Sandoz TH-40 (CAS Registry No.        32694-95-4),    -   xanthylium, 3,6-bis(diethylamino)-9-(2,4-disulfophenyl)-, inner        salt, sodium salt, also known as Sulforhodamine B (CAS Registry        No. 3520-42-1, aka Acid Red 52),    -   benzenesulfonic acid,        2,2′-(1,2-ethenediyl)bis[5-[[4-[(aminomethyl)(2-hydroxyethyl)amino]-6-(phenylamino)-1,3,5-triazin-2-yl]amino]-,        disodium salt, also known as Tinopal 5BM-GX (CAS Registry No.        169762-28-1),    -   Tinopol DCS (CAS Registry No. 205265-33-4),    -   benzenesulfonic acid,        2,2′-([1,1′-biphenyl]-4,4′-diyldi-2,1-ethenediyl)bis-, disodium        salt, also known as Tinopal CBS-X (CAS Registry No. 27344-41-8),    -   benzenesulfonic acid,        5-(2H-naphtho[1,2-d]triazol-2-yl)-2-(2-phenylethenyl)-, sodium        salt, also known as Tinopal RBS 200, (CAS Registry No.        6416-68-8),    -   7-benzothiazolesulfonic acid,        2,2′-(1-triazene-1,3-diyldi-4,1-phenylene)bis[6-methyl-,        disodium salt, also known as Titan Yellow (CAS Registry No.        1829-00-1, aka Thiazole Yellow G), and    -   all ammonium, potassium and sodium salts thereof, and all like        agents and suitable mixtures thereof.

The more preferred fluorescent inert tracers of the present inventioninclude 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt (CAS RegistryNo. 59572-10-0); 1,5-naphthalenedisulfonic acid disodium salt (hydrate)(CAS Registry No. 1655-29-4, aka 1,5-NDSA hydrate); xanthylium,9-(2,4-dicarboxyphenyl)-3,6-bis(diethylamino)-, chloride, disodium salt,also known as Rhodamine WT (CAS Registry No. 37299-86-8);1-deoxy-1-(3,4-dihydro-7,8-dimethyl-2,4-dioxobenzo[g]pteridin-10(2H)-yl)-D-ribitol,also known as Riboflavin or Vitamin B2 (CAS Registry No. 83-88-5);fluorescein (CAS Registry No. 2321-07-5); fluorescein, sodium salt (CASRegistry No. 518-47-8, aka Acid Yellow 73, Uranine);2-anthracenesulfonic acid sodium salt (CAS Registry No. 16106-40-4);1,5-anthracenedisulfonic acid (CAS Registry No. 61736-91-2) and saltsthereof; 2,6-anthracenedisulfonic acid (CAS Registry No. 61736-95-6) andsalts thereof; 1,8-anthracenedisulfonic acid (CAS Registry No.61736-92-3) and salts thereof; and mixtures thereof. The fluorescenttracers listed above are commercially available from a variety ofdifferent chemical supply companies.

The most preferred inert fluorescent tracer compound is1,3,6,8-pyrenetetrasulfonic acid, sodium salt.

The cationic terpolymer/inert fluorescent tracer compound composition isprepared by adding the inert fluorescent tracer compound with stirringto the cationic terpolymer of this invention. An inverting surfactant asdescribed herein may be added along with the inert fluorescent tracercompound. The amount of inert fluorescent tracer compound added may bereadily determined by one of ordinary skill in the art, taking intoconsideration the polymer composition and the characteristics of thesludge being treated.

One or more fluorometers are used to detect the fluorescent signal ofthe inert fluorescent tracers. Suitable fluorometers are selected fromthe group comprising Examples of fluorometers that may be used in thepractice of this invention include the TRASAR® 3000 fluorometer, theTRASAR® 8000 fluorometer and the TRASAR® XE-2 Controller, which includesa fluorometer with integrated controller, all available from Nalco; theHitachi F-4500 fluorometer (available from Hitachi through HitachiInstruments Inc. of San Jose, Calif.); the JOBIN YVON FluoroMax-3 “SPEX”fluorometer (available from JOBIN YVON Inc. of Edison, N.J.); and theGilford Fluoro-IV spectrophotometer or the SFM 25 (available fromBio-tech Kontron through Research Instruments International of SanDiego, Calif.). It should be appreciated that the fluorometer list isnot comprehensive and is intended only to show examples of fluorometers.Other commercially available fluorometers and modifications thereof canalso be used in this invention.

After the fluorometer has been used to detect the fluorescent signal ofthe inert fluorescent tracer then the detected fluorescent signal can beconverted into the actual concentration of inert fluorescent tracerusing graphs that show what the detected fluorescent signal is for aspecific amount of a specific inert fluorescent tracer. These graphs areknown to people of ordinary skill in the art of fluorometry.

Because the inert fluorescent tracer is added to the screen bowlcentrifuge in a known proportion to the cationic terpolymer, bydetecting the fluorescent signal of the inert fluorescent tracer it ispossible to calculate the amount of cationic terpolymer present eitherin the screen bowl centrifuge or in the effluent or even in the screendrain. This enables the operator to determine whether the correct amountof cationic terpolymer is present and even to determine where it ispresent. If desired, adjustments to the operating conditions of thescreenbowl centrifuge can be made to ensure the amount of cationicterpolymer present is what is supposed to be present.

The third aspect of the instant claimed invention is the method of thefirst aspect of the instant claimed invention wherein an inertfluorescent tracer is added to the cationic terpolymer and one or morefluorometers are used to detect the fluorescent signal of the inertfluorescent tracer, which fluorescent signal is used to determine howmuch inert fluorescent tracer is present and that information is used todetermine how much cationic terpolymer is present and by knowing howmuch cationic terpolymer is present then if desired, adjustments to theoperating conditions of the screenbowl centrifuge can be made to ensurethe desired amount of cationic terpolymer is present.

The fourth aspect of the instant claimed invention is the method of thesecond aspect of the instant claimed invention wherein an inertfluorescent tracer is added to the cationic terpolymer and one or morefluorometers are used to detect the fluorescent signal of the inertfluorescent tracer, which fluorescent signal is used to determine howmuch inert fluorescent tracer is present and that information is used todetermine how much cationic terpolymer is present and by knowing howmuch cationic terpolymer is present, then if desired, adjustments to theoperating conditions of the screenbowl centrifuge can be made to ensurethe desired amount of cationic terpolymer is present.

The fifth aspect of the instant claimed invention is the method of thethird aspect wherein an inert fluorescent tracer is added to thecationic terpolymer and one or more fluorometers are used to detect thefluorescent signal of the inert fluorescent tracer, which fluorescentsignal is used to determine how much inert fluorescent tracer is presentand that information is used to determine how much cationic terpolymeris present and by knowing how much cationic terpolymer is present, thenif desired, adjustments to the operating conditions of the screenbowlcentrifuge can be made to ensure the desired amount of cationicterpolymer is present.

The following examples are intended to be illustrative of the presentinvention and to teach one of ordinary skill how to make and use theinvention. These examples are not intended to limit the invention or itsprotection in any way.

EXAMPLE 1

The screening test for the cationic terpolymers in the method of theinstant claimed invention is as follows:

A mixture of 40 cc of slurry and cationic terpolymer, at the desireddose, is charged into a 50 mL centrifuge tube. The contents of the tubeare mixed on a Fisher Vortex Genie 2™ from Fisher Scientific, dialed to6.5 of 8 for 10 seconds. This vortex mixing is followed bycentrifugation, using a Model HN-S centrifuge from InternationalEquipment Company, Needham Heights, Mass., set at Full, which reads as2700 revolutions per minute on the tach dial for 1 min. After one minutethe centrifuge is ‘dialed off’ and the break is applied. Followingcentrifugation, the contents of the tube are mixed again for 10 secondswith the same vortex mixer used previously at the same settings, atwhich time the nature of the floc formed is observed.

In this screening study a coal slurry is used. The cationic polymers areas follows:

-   -   Polymer A is 70 mol percent AM/29 mol percent DMAEA.MCQ/1 mol        percent HEMA,    -   Polymer B is 49 mol percent AM/49 mol percent DMAEA.MCQ/2 mol        percent HEMA,

Polymer C is 34 mol percent AM/64 mol percent DMAEA.MCQ/2 mol percentHEMA. Mole % lbs active product Observations @ 10 Additional ExamplePolymer Charge per dry ton of coal seconds Observations 1 A 30 0.4 Clearsupernatant, Completely “flocked”. Compacted flock held together 2 A 300.4 Compaction broke up after 10 seconds. Very fine flocks 3 C 65 0.4Clear supernatant, Completely “flocked”. Compacted flock held together 4C 65 0.4 Clear supernatant, Held together until after an Completely“flocked”. additional 35 seconds, Compacted flock held dislodged largeflocks. Left together half the “cake” 5 C 65 0.4 Very small amount ofHeld together until after medium sized after 9 an additional 21 seconds,most of seconds, then broke and flocked coal remained blackened water.Left compacted third of “cake” 6 C 65 0.4 Clear supernatant, Very smallamount of Completely “flocked”. medium sized after 11 Compacted flockheld seconds. Held together together until after an additional 31seconds, then broke and blackened water. Left third of “cake” 7 C 65 0.4Very small amount of Held together until after medium sized after 8 anadditional 18 seconds, most of seconds, then broke. flocked coalremained Left two thirds of “cake” compacted 8 B 50 0.4 In two runs,Compaction broke up after 5-7 seconds.

The observations recorded in this table show that the indicated cationicterpolymers are effective in flocculating the coal in the slurry underthe harsh vibration-centrifugation-vibration conditions of the test.

By using this screening test, it is found that polymers that performwell in high-shear field applications are those that have the ability toform a large floc when mixed on the vortex mixer prior to and followingcentrifugation.

In a large scale coal processing plant for example, the recovered finecoal is saleable and would afford an additional source of revenue. As anexample, a typical coal production plant site can process about 6,000tons/day through the screen bowl centrifuges. The improvement ineffluent solids described here would afford about 150 tons/day,currently saleable at about $15-$30/ton.

Various changes and modifications to the presently preferred embodimentsdescribed herein will be apparent to those skilled in the art. Suchchanges and modifications can be made without departing from the spiritand scope of the present invention and without diminishing its attendantadvantages. It is therefore intended that such changes and modificationsbe covered by the appended claims.

1. A method of enhancing the recovery of useful coal from screenbowl centrifuge separation operations comprising adding to the screenbowl centrifuge, from about 0.03 lbs active polymer/ton dry solids in centrifuge to about 0.70 lbs active polymer/ton dry solids in centrifuge, of a cationic terpolymer, wherein said cationic terpolymer is prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.1 to about 10 mole percent of one or more hydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent of one or more nonionic monomers.
 2. The method of claim 1 wherein the nonionic monomers present in the cationic terpolymer are selected from acrylamide and methacrylamide and the cationic monomers are selected from dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, acrylamidopropyltrimethylammonium chloride and methacrylamidopropyltrimethylammonium chloride.
 3. The method of claim 2 wherein the hydroxyalkyl(meth)acrylate present in the cationic terpolymer is selected from hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and 6-hydroxyhexyl methacrylate.
 4. The method of claim 1 wherein the cationic terpolymer is prepared by polymerizing from about 20 to about 80 mole percent of one or more cationic monomers, from about 1 to about 2.5 mole percent of one or more hydroxyalkyl(meth)acrylates and from 17.5 to about 79 mole percent of one or more nonionic monomers.
 5. The method of claim 4 wherein the nonionic monomer present in the cationic terpolymer is acrylamide and the cationic monomer present in the cationic terpolymer is dimethylaminoethyl acrylate methyl chloride quaternary salt.
 6. The method of claim 5 wherein the hydroxyalkyl(meth)acrylate present in the cationic terpolymer is 2-hydroxyethyl methacrylate.
 7. A method of enhancing the recovery of useful potassium chloride from screenbowl centrifuge separation operations comprising adding to the screenbowl centrifuge, from about 0.03 lbs active polymer/ton dry solids in centrifuge to about 0.70 lbs active polymer/ton dry solids in centrifuge, of a cationic terpolymer, wherein said cationic terpolymer is prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.1 to about 10 mole percent of one or more hydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent of one or more nonionic monomers.
 8. The method of claim 7 wherein the nonionic monomers present in the cationic terpolymer are selected from acrylamide and methacrylamide and the cationic monomers are selected from dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, acrylamidopropyltrimethylammonium chloride and methacrylamidopropyltrimethylammonium chloride.
 9. The method of claim 7 wherein the hydroxyalkyl(meth)acrylate present in the cationic terpolymer is selected from hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and 6-hydroxyhexyl methacrylate.
 10. The method of claim 7 wherein the cationic terpolymer is prepared by polymerizing from about 20 to about 80 mole percent of one or more cationic monomers, from about 1 to about 2.5 mole percent of one or more hydroxyalkyl(meth)acrylates and from 17.5 to about 79 mole percent of one or more nonionic monomers.
 11. The method of claim 7 wherein the nonionic monomer present in the cationic terpolymer is acrylamide and the cationic monomer present in the cationic terpolymer is dimethylaminoethyl acrylate methyl chloride quaternary salt and the hydroxyalkyl(meth)acrylate present in the cationic terpolymer is 2-hydroxyethyl methacrylate.
 12. A method of enhancing the recovery of useful borax from screenbowl centrifuge separation operations comprising adding to the screenbowl centrifuge, from about 0.03 lbs active polymer/ton dry solids in centrifuge to about 0.70 lbs active polymer/ton dry solids in centrifuge, of a cationic terpolymer, wherein said cationic terpolymer is prepared by polymerizing from about 1 to about 99.1 mole percent of one or more cationic monomers, from about 0.1 to about 10 mole percent of one or more hydroxyalkyl(meth)acrylates and from one to about 98.1 mole percent of one or more nonionic monomers.
 13. The method of claim 12 wherein the nonionic monomers present in the cationic terpolymer are selected from acrylamide and methacrylamide and the cationic monomers are selected from dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, acrylamidopropyltrimethylammonium chloride and methacrylamidopropyltrimethylammonium chloride.
 14. The method of claim 12 wherein the hydroxyalkyl(meth)acrylate present in the cationic terpolymer is selected from hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and 6-hydroxyhexyl methacrylate.
 15. The method of claim 12 wherein the cationic terpolymer is prepared by polymerizing from about 20 to about 80 mole percent of one or more cationic monomers, from about 1 to about 2.5 mole percent of one or more hydroxyalkyl(meth)acrylates and from 17.5 to about 79 mole percent of one or more nonionic monomers.
 16. The method of claim 12 wherein the nonionic monomer present in the cationic terpolymer is acrylamide and the cationic monomer present in the cationic terpolymer is dimethylaminoethyl acrylate methyl chloride quaternary salt and the hydroxyalkyl(meth)acrylate present in the cationic terpolymer is 2-hydroxyethyl methacrylate.
 17. The method of claim 1 wherein an inert fluorescent tracer is added to the cationic terpolymer and one or more fluorometers are used to detect the fluorescent signal of the inert fluorescent tracer, which fluorescent signal is used to determine how much inert fluorescent tracer is present and that information is used to determine how much cationic terpolymer is present and by knowing how much cationic terpolymer is present then if desired, adjustments to the operating conditions of the screenbowl centrifuge can be made to ensure the desired amount of cationic terpolymer is present.
 18. The method of claim 7 wherein an inert fluorescent tracer is added to the cationic terpolymer and one or more fluorometers are used to detect the fluorescent signal of the inert fluorescent tracer, which fluorescent signal is used to determine how much inert fluorescent tracer is present and that information is used to determine how much cationic terpolymer is present and by knowing how much cationic terpolymer is present, then if desired, adjustments to the operating conditions of the screenbowl centrifuge can be made to ensure the desired amount of cationic terpolymer is present.
 19. The method of claim 12 wherein an inert fluorescent tracer is added to the cationic terpolymer and one or more fluorometers are used to detect the fluorescent signal of the inert fluorescent tracer, which fluorescent signal is used to determine how much inert fluorescent tracer is present and that information is used to determine how much cationic terpolymer is present and by knowing how much cationic terpolymer is present, then if desired, adjustments to the operating conditions of the screenbowl centrifuge can be made to ensure the desired amount of cationic terpolymer is present. 